SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.short_description, 
  IF(
    cscart_product_descriptions.short_description = '' 
    OR cscart_product_descriptions.short_description IS NULL, 
    cscart_product_descriptions.full_description, 
    ''
  ) AS full_description 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    84708, 84749, 84731, 84732, 84733, 87921, 
    87923, 87933, 87935, 88042, 84720, 
    84723, 84727, 87974, 84271, 84939, 
    84734, 84735, 84938, 84719, 84722, 
    84724, 84744, 84718, 84721, 84937, 
    84936, 87991, 87966, 87922, 87928, 
    87934, 88017, 84856, 84857, 84949, 
    84950, 84690, 84748, 88039, 87905, 
    84691, 87894, 84847, 84854, 84855, 
    87906, 84689
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00091

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "21.63"
    },
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "range",
      "possible_keys": [
        "PRIMARY",
        "product_id"
      ],
      "key": "PRIMARY",
      "used_key_parts": [
        "product_id",
        "lang_code"
      ],
      "key_length": "9",
      "rows_examined_per_scan": 48,
      "rows_produced_per_join": 48,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "16.83",
        "eval_cost": "4.80",
        "prefix_cost": "21.63",
        "data_read_per_join": "183K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`nuie_scalesta_net`.`cscart_product_descriptions`.`product_id` in (84708,84749,84731,84732,84733,87921,87923,87933,87935,88042,84720,84723,84727,87974,84271,84939,84734,84735,84938,84719,84722,84724,84744,84718,84721,84937,84936,87991,87966,87922,87928,87934,88017,84856,84857,84949,84950,84690,84748,88039,87905,84691,87894,84847,84854,84855,87906,84689)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}